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Commit be1c6341 authored by Olaf Kirch's avatar Olaf Kirch Committed by Jens Axboe
Browse files

[PATCH] blktrace: add timestamp message 



This adds a new timestamp message to blktrace, giving the timeofday when
we starting tracing. This helps user space correlate block trace events
with eg an application strace.

This requires a (compatible) update to blkparse. The changed blkparse
is still able to process traces generated by older kernels, and older
versions of blkparse should silently ignore the new records (because
they have a pid of 0).

Signed-off-by: default avatarOlaf Kirch <okir@suse.de>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 0215ffb0

block/blktrace.c

+45 −12
Original line number Diff line number Diff line
@@ -22,30 +22,61 @@ 
#include <linux/init.h>

#include <linux/mutex.h>

#include <linux/debugfs.h>

#include <linux/time.h>

#include <asm/uaccess.h>



static DEFINE_PER_CPU(unsigned long long, blk_trace_cpu_offset) = { 0, };

static unsigned int blktrace_seq __read_mostly = 1;



/*

 * Send out a notify for this process, if we haven't done so since a trace

 * started

 * Send out a notify message.

 */

static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)

static inline unsigned int trace_note(struct blk_trace *bt,

		pid_t pid, int action,

		const void *data, size_t len)

{

	struct blk_io_trace *t;

	int cpu = smp_processor_id();



	t = relay_reserve(bt->rchan, sizeof(*t) + len);

	if (t == NULL)

		return 0;



	t = relay_reserve(bt->rchan, sizeof(*t) + sizeof(tsk->comm));

	if (t) {

	t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;

	t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu);

	t->device = bt->dev;

		t->action = BLK_TC_ACT(BLK_TC_NOTIFY);

		t->pid = tsk->pid;

		t->cpu = smp_processor_id();

		t->pdu_len = sizeof(tsk->comm);

		memcpy((void *) t + sizeof(*t), tsk->comm, t->pdu_len);

		tsk->btrace_seq = blktrace_seq;

	t->action = action;

	t->pid = pid;

	t->cpu = cpu;

	t->pdu_len = len;

	memcpy((void *) t + sizeof(*t), data, len);

	return blktrace_seq;

}



/*

 * Send out a notify for this process, if we haven't done so since a trace

 * started

 */

static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)

{

	tsk->btrace_seq = trace_note(bt, tsk->pid,

			BLK_TN_PROCESS,

			tsk->comm, sizeof(tsk->comm));

}



static void trace_note_time(struct blk_trace *bt)

{

	struct timespec now;

	unsigned long flags;

	u32 words[2];



	getnstimeofday(&now);

	words[0] = now.tv_sec;

	words[1] = now.tv_nsec;



	local_irq_save(flags);

	trace_note(bt, 0, BLK_TN_TIMESTAMP, words, sizeof(words));

	local_irq_restore(flags);

}



static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
@@ -394,6 +425,8 @@ static int blk_trace_startstop(request_queue_t *q, int start) 
			blktrace_seq++;

			smp_mb();

			bt->trace_state = Blktrace_running;



			trace_note_time(bt);

			ret = 0;

		}

	} else {

include/linux/blktrace_api.h

+12 −0
Original line number Diff line number Diff line
@@ -49,6 +49,15 @@ enum blktrace_act { 
	__BLK_TA_REMAP,			/* bio was remapped */

};



/*

 * Notify events.

 */

enum blktrace_notify {

	__BLK_TN_PROCESS = 0,		/* establish pid/name mapping */

	__BLK_TN_TIMESTAMP,		/* include system clock */

};





/*

 * Trace actions in full. Additionally, read or write is masked

 */
@@ -68,6 +77,9 @@ enum blktrace_act { 
#define BLK_TA_BOUNCE		(__BLK_TA_BOUNCE)

#define BLK_TA_REMAP		(__BLK_TA_REMAP | BLK_TC_ACT(BLK_TC_QUEUE))



#define BLK_TN_PROCESS		(__BLK_TN_PROCESS | BLK_TC_ACT(BLK_TC_NOTIFY))

#define BLK_TN_TIMESTAMP	(__BLK_TN_TIMESTAMP | BLK_TC_ACT(BLK_TC_NOTIFY))



#define BLK_IO_TRACE_MAGIC	0x65617400

#define BLK_IO_TRACE_VERSION	0x07